In an optical communication system, it is generally necessary to couple an optical fiber to an opto-electronic transmitter, receiver or transceiver system and, in turn, to couple that opto-electronic system to an external electronic system such as a switching system or processing system. These connections can be facilitated by modularizing the transceiver or other opto-electronic system. A modularized opto-electronic transceiver system includes an opto-electronic light source, such as a laser, and an opto-electronic light receiver, such as a photodiode, and may also include various electronic circuitry associated with the laser and photodiode. For example, driver circuitry can be included for driving the laser in response to electronic signals received from the external electronic system. Receiver circuitry can be included for processing the signals produced by the photodiode and providing output signals to the external electronic system. One or more lenses are also commonly included.
In an opto-electronic transceiver module, the light source, light receiver, or transceiver (opto-electronic device) is commonly mounted on a substrate, such as a printed circuit board (PCB), and electrically connected by wirebonds to pads on the PCB. However, wirebonds suffer from disadvantages including parasitic effects and susceptibility to noise that can impact data transfer speed.
So-called “flip-chip” mounting is a known alternative to wirebonding. In flip-chip mounting, solder bumps are deposited on conductive pads on the upper surface of the chip (i.e., semiconductor die) during the final wafer processing step of the chip fabrication process. After the chip has been separated from the wafer (via the process known as dicing), the chip can be mounted on a substrate by inverting or flipping the chip over so that the solder bumps on its upper surface align with and make contact with corresponding conductive pads on the upper surface of the substrate. A reflow soldering process is then used to attach the solder bumps of the chip to the conductive pads of the substrate.
It has been suggested to employ flip-chip mounting in an opto-electronic module by mounting an opto-electronic device on the surface of a substrate such as a PCB over an aperture in the PCB, with the upper surface of the opto-electronic device facing the upper surface of the PCB. Electrical connections are made between solder bumps on the upper surface of the opto-electronic device and conductive pads on the upper surface of the PCB. In operation, optical signals can be communicated through the aperture in the PCB between the opto-electronic device and an external system below the PCB. There are various disadvantages to having to provide an aperture or other optical path through a PCB or similar substrate.
It would be desirable to employ flip-chip mounting in an opto-electronic system without having to provide an optical signal path through a PCB or other substrate on which the opto-electronic device of the system is mounted.